So called Femto Base Transceiver Stations, Femto BTS, are being developed in order to provide GSM and/or WCDMA coverage for end users in limited coverage areas, e.g. private homes or offices. A Femto BTS in a GSM system will typically be connected to a Femto Base Station Controller, BSC, and in the WCDMA case there will usually be a Femto Radio Network Controller, Femto RNC, for the Femto BTS.
Another system which is currently under development is the Long Term Evolution project, LTE, which is being developed in order to provide higher bit rates and capacity for packet switched services. An LTE BTS may be a separate base station, or it may be combined with a base station from another system, such as GSM or WCDMA.
For both Femto and LTE BTSs, there is thus a high likelihood of “joint coverage” with another system, such as GSM or WCDMA, since both Femto BTSs and LTE BTSs may be deployed within or adjacent to such cells, and may in fact, at least in the Femto case, share the physical BSC or RNC with a GSM or WCDMA system.
As explained above, there may thus in future networks be coexistence between cells of different kinds, e.g. GSM or WCDMA with Femto or LTE cells. This coexistence places specials demands on the frequency planning in the network. For example, the Femto concept as such will require a particularly robust way of handling the frequency planning in networks with “shared systems”, i.e. both Femto and GSM or WCDMA, since it is possible that users may be able to purchase Femto BTSs “over the counter” and deploy them wherever the user deems necessary and/or desirable, in some cases even without the prior consent of the operator of the larger network, e.g. GSM or WCDMA.
In networks where there is coexistence between GSM and/or WCDMA and LTE systems, there will also be a special need for elaborate frequency planning.